1. Field of the Invention
The present invention relates to a glass frit for dielectrics, a dielectric ceramic composition, a multilayer ceramic capacitor, and a method for manufacturing the same. More particularly, the present invention relates to a glass frit for dielectrics, which has a higher ratio of tetracoordinate boron in a lithium borosilicate glass, thereby preventing gelation of dielectric slurries while minimizing or preventing agglomeration of the glass on the surface of a dielectric layer of a multilayer ceramic capacitor.
2. Description of the Related Art
Recently, as a result of an increasing trend toward miniaturization and weight reduction of electronic devices, use of multilayer ceramic capacitors has been increased. The multilayer ceramic capacitors are generally used for mobile communication devices, such as mobile phones, notebook computers, PDAs, and the like.
The multilayer ceramic capacitor generally comprises a plurality of dielectric layers, internal electrodes formed between the dielectric layers, and external electrodes formed at opposite ends of a stacked body so as to be electrically connected to the internal electrodes. The internal electrodes of the ceramic capacitor are formed of inexpensive Ni, Cu, or alloys thereof instead of high priced Pd. In particular, it has been attempted to employ Cu exhibiting less variation in resistance and capacitance for the internal electrodes of a multilayer ceramic capacitor for temperature compensation. However, since Cu has a lower melting point, it has been needed to develop a new dielectric ceramic composition, which enables sintering at a low temperature of 1,000° C. or less.
Technology of the multilayer ceramic capacitor for temperature compensation enabling low temperature sintering is disclosed in Japanese Patent Laid-open Publication Nos. 1999-283860 and 2002-356371, and Korean Patent Laid-open Publication No. 2001-0048867. The technology of the disclosures provides a dielectric ceramic composition comprising a glass frit in order to employ Cu for the internal electrodes.
First, Japanese Patent Laid-open Publication No. 1999-283860 discloses a multilayer ceramic capacitor comprising dielectric ceramic layers, in which the dielectric ceramic layers comprise 100 parts by weight of Ca(Zr1-yTiy)O3 as a main component, 0.5˜2.5 parts by weight of aSiO2-bB2O3-eCaO based glass (25≦a≦45, 45≦b≦65, 5≦e≦20), and 1.0˜3.0 parts by weight of MnCO3 as a Mn compound.
Japanese Patent Laid-open Publication No. 2002-356371 discloses a multilayer ceramic capacitor comprising dielectric ceramic layers, in which the dielectric ceramic layers comprise 100 parts by weight of (Ca1-xMgx)(Zr1-yTiy)O3 as a main component, 0.5˜2.5 parts by weight of aSiO2-bB2O3-cLi2O-eCaO-iBaO based glass (0.1≦a≦0.7, 0.15≦b≦0.89, 0.01≦c≦0.5, 0≦d≦0.4, 0≦i≦0.4), and MnO2.
Korean Patent Laid-open Publication No. 2001-0048867 discloses a multilayer ceramic capacitor comprising dielectric ceramic layers, in which the dielectric ceramic layers comprise 1˜5 parts by weight of MnO2, 0.5˜10 parts by weight of aSiO2-bB2O3-cLi2O-fAl2O3-iRO-jRO2 based glass (10≦a≦50, 10≦b≦60, 10≦c≦50, 0<f≦10, 0<i+j≦25), and the balance of (Ca1-xSrx)(Zr1-yTiy)O3 (0≦x≦0.1, 0≦y≦0.1). In the glass, R represents one element selected from Ba, Ca, Sr, Mn, Mg, Zn, Ti, Pb and Ce.
With the conventional technology of the disclosures, the glass frit is added to the dielectric ceramic composition, thereby realizing low temperature sintering. However, when combining the glass frit with ceramic slurries, gelation of the slurries occurs long after mixing of the slurries, thereby making it difficult to apply the technology to mass production of the multilayer ceramic capacitors. Moreover, the conventional technology of the disclosures has a problem in that, due to variation in composition caused by elution or volatilization of some components of the glass from the ceramic slurries, fluidity of the glass is lowered, causing agglomeration of the glass on the surface of a ceramic sintered body. Additionally, the multilayer ceramic capacitor manufactured by the conventional technology of the disclosures exhibits poor acid resistance.